I used this technique as you mentioned and my hopes were high as for the first time, I could see few data columns from expand section. I selected few data coloumns of my choice, and when i tried to save and close the query. they asked me to login to my salesforce account. Once I did that. it sent me message
you are already signed in
' access to the resource is forbidden". Sign in as a diff user.
I was having the same issue with (August 2018 version). Installed the September 2018 version (Version: 2.62.5222.601) and Salesforce Reports are working again. Hope it works for you as well.